Ultrastructural and radiotracer studies of pore function in foraminifera

Clusters of mitochondria have been observed close to the inner end of the pores in Nonionella stella, Globobulimina pacifica, Buliminella tenuata, Bolivina argentea, Loxostomum pseudobeyrichi, Cassidulinoides cornuta and Bolivina cf. subexcavata, pointing to a pore function of oxygen-uptake. The relationship between mitochondria and pores is most distinct in Buliminella tenuata, Bolivina argentea and L. pseudobeyrichi collected from a deep-water, low-oxygen environment. Amphistegina lobifera Larsen, 1976 readily took up 14CO2 through its pores, indicating a pore function related to the photosynthetic activities of its symbionts. 14C-labelled glucose did not pass through the pores in traceable amounts during a 2 h exposure time.